Electrical transformers are typically used to distribute electrical power from main utility lines for secondary distribution. The transformer accepts the main utility line on the primary side of the transformer and distributes the power from a secondary side of the transformer. An electrical step-down is provided by the transformer so as to provide for the proper secondary distribution of electrical power for residential and commercial use.
The transformer is normally housed in a steel cabinet. A threaded copper stud extends from the secondary side of the transformer from which secondary distribution is provided. Plural electrical conductors, connected to the threaded stud, provide for distribution of power to the end user.
In order to connect the conductor to the stud, a transformer stud connector is employed. These transformer stud connectors are elongate, electrically conductive members which are inserted over the copper stud extending from the secondary side of the transformer. The stud connector may be threadingly attached to the transformer stud. Extending longitudinally therefrom are a plurality of conductor accommodating ports wherein the ends of conductors may be inserted. Each conductor port has an associated set screw to effect mechanical and electrical connection to the transformer stud connector. Examples of transformer stud connectors are shown in U.S. Pat. Nos. 5,931,708; 5,848,913; 5,690,516; DES 377,782; DES 346,150; and DES 309,664.
In a typical arrangement, the utility distribution transformer has threaded studs typically ⅝-11 or 1-14, oversized applications can have larger 1¼-12, 1½-12 threaded studs or possibly a custom size dictated by customer needs. A connector, sometimes referred to as a bus bar, is used to connect to the stud and provide ports for multiple wire connections. The connector is threaded with the same pitch tread but the threaded hole is equal or larger to the diameter of the transformer stud. This allows the connector to be slipped on to the stud, known as a slip fit connector, instead of being spun onto the treaded shaft. This allows the connector to be installed and removed without having to remove any of the conductors. An orthogonally mounted set screw is typically used to secure the connector to the studded shaft. However, slip fit connectors, due to the presence of threads around the inside of the stud hole can sometime be difficult to remove from the stud. In many cases, once the setscrews securing the connector are loosened, the connector must still be wiggled up and down or side to side to get the connector to slide off. This can make removal of the connector a difficult and time consuming process as well as damaging the connector and stud threads by repeated contact between the threads while trying to wiggle the connector off of the stud. This problem can be exacerbated when the connector is adapted to receive more than one size stud due to the close tolerances that are required for the stud connector hole when more than one size stud can be accommodated within the connector.
In prior art connectors, various means were provided so that a single connector could be used to service studs of various sizes. One way is to provide at least two threaded holes, one for each of the stud sizes serviced by the connector. However, the disadvantage of such design is that it requires at least two holes, and therefore needs to be larger than necessary. Also, because by design the stud hole has to meet a certain depth to accommodate the stud, the portion of the connector receiving the threaded stud in not usable for conductor connections, thus additionally requiring a longer connector to accommodate an equal number of conductors. This problem is exacerbated for connectors having multiple threaded holes. In addition, a multi hole connector does not address the problems of easy installation and removal.
A further prior art design utilizes a tear-drop design of two holes which overlap and therefore produce a large diameter threaded hole having an arc-section of a smaller hole at the bottom of the larger hole, which extends beyond the perimeter of the larger hole. The disadvantage of this design is that it requires pre-drilling a smaller hole, followed by drilling of the second larger hole, partially overlapping the smaller hole. Alternately, the larger hole can be bored first, followed by milling or broaching of the bottom arc section to create the “tear-drop”. Both methods therefore require a two-step process, which adds complexity and expense to the manufacturing process.
A third alternative prior art design utilizes a slider system mounted to the connector which has grooved sides at various levels on the connector body. By moving the slider, in the grooves, various gap sizes between the slider and the connector body can be formed. However, this design requires a second element, the slider, to be added to the connector, which adds complexity and expense to the manufacturing process.
It is therefore desirable to provide a transformer stud connector, which can be mounted on studs of various sizes without the complexity, or cost of prior art designs, has a more compact design, provides greater physical contact between the connector and the stud and provides for easy installation and removal of the connector with out extra effort or steps on the part of the user.